1. Field of the Invention
This invention relates to an optical disk and an optical disk recording apparatus and method. The invention is more particularly related to the determination of optimum recording power for an optical disk. The invention is further related to the determination of an optimum power for making recordings by performing test recordings in test areas on an optical disk and determining optimum recording power throughout the recording area based on the test recordings. The invention is still further related to determining optimum recording power throughout a modified constant linear velocity (ZCLV) formatted optical disk by making multiple test recordings in an area of the ZCLV formatted optical disk corresponding to the recording characteristics of the entire disk and determining optimum recording power based on the test recordings.
2. Discussion of the Background
Throughout the history of the development of storage devices, design engineers have strived to increase capacity and speed of storage devices. Current industry efforts are directed towards storage on optical disks. Increasing pressure for development of fast, high capacity optical disks is being levied by, among others, the motion picture industry, the music recording industry, and a wide range of computer application developers.
In the development of an optical storage device, design engineers are faced with the challenge whereby the storage device must determine and apply an amount of power in order for the device to make recordings. If not enough power is applied, recordings will either be ineffective or flawed. Applying too much power can create similar problems and is less energy efficient.
A current industry standard to determine an optimum recording power level for an optical disk is described in the standard CD-WO (Compact Disk Write Once) in the Orange Book Part 2. As described therein, with CD-WO, also known as Optimum Power Control (OPC), an industry adopted power optimizing method for laser recording on an optical disk is provided. OPC is a technique for determining an optimum recording power for an optical disk media and optical driving apparatus combination before data recording is executed.
The procedure of OPC is to first read a value of a recommended recording power (P0) which is recorded on the optical disk. Next, a test recording is executed wherein data is recorded utilizing several levels of recording power based on the recommended recording power (P0). These test recordings are performed in a power calibration area (PCA) of the optical disk. Based on the reproduction of the test data thus recorded, an optimum recording power for the optical disk is determined. The power calibration area (PCA) is also commonly referred to as an optimum power control (OPC) area.
CD-WO is a constant linear velocity (CLV) disk. With a CLV disk, the linear velocity at which recording and reading operations are performed is constant regardless of which track on the disk is being recorded or read. Because the CD-WO disk is maintained at a constant linear velocity, recording characteristics are constant throughout the entire disk. Thus, a PCA is maintained in one area positioned in an inner area of a data recording area of the CD-WO disk.
Japanese Laid-Open Patent Nos. 1995-235,057 and 1995-287,847 each detail methods of OPC with increased accuracy over the Orange Book Part 2 standard. In these methods, the PCA of a CD-WO disk is divided into small plural areas in which the OPC procedure is executed more times, thus providing increased accuracy. In Orange Book Part 2, PCA utilizes a unit of 15 frames for a test recording, while within the OPC methods in the above-mentioned Japanese Laid-Open Patents, PCA utilizes a unit of 5 frames thereby allowing room for additional test recordings. The method thus described results in more accurate OPC and recording frequency as compared with the standardized method in the OPC Orange Book Part 2. The above method is applied to a constant linear velocity disk (CLV) and therefore, as described above, the PCA is in only in one area of the disk.
Thus far we have discussed optical disks applying a constant linear velocity (CLV) format for rotation of the optical disk. Another rotational format, known as modified constant linear velocity (MCLV or ZCLV) is also popular. A ZCLV formatted disk is divided into plural zones and is rotated at a constant angular velocity (CAV) within each zone. The angular velocity of the ZCLV disk changes as the disk is recorded or read in different zones.
FIG. 1A is a schematic view showing a disk format applied to a modified constant linear velocity optical disk, ZCLV disk 1. In FIG. 1A, the ZCLV disk 1 has two zones, an inner zone 3 and an outer zone 5. FIG. 1A also illustrates a sector 7 of the ZCLV disk 1 which is one of many sectors composing each zone on the ZCLV disk 1. FIG. 1B illustrates the inner zone 3, FIG. 1C illustrates the outer zone 5, and FIG. 1D highlights sector 7 showing multiple tracks 9 found in each zone throughout the ZCLV disk 1. The ZCLV disk 1 may also be formatted in multiple zones (zones 1-4, for example) as illustrated in FIG. 1E.
In ZCLV, a recording area is divided into plural zones (inner zone 3 and outer zone 5 of FIG. 1A, for example) and the disk rotates at a constant angular velocity (CAV) within each zone. When a recording area of a disk changes from one zone to another (from inner zone 3 to outer zone 5, for example), the angular velocity of the disk changes according to the new recording zone. Also, a linear velocity of an innermost track in each zone is at a reference linear velocity Vr. Therefore, the linear velocity of tracks within each zone of a ZCLV formatted disk start at a reference linear velocity Vr and increase throughout the zone.
The various velocities and features of a ZCLV formatted disk are shown in FIGS. 2A-2D. FIG. 2A is a graph showing the angular velocity of ZCLV disk 1 with reference to four zones (zone 1, zone 2, zone 3, and zone 4). The angular velocity of the ZCLV disk 1 is stepped incrementally for each zone, the inner zones (zone 1 and zone 2) being at a higher angular velocity than the outer zones (zone 3 and zone 4). For further reference, a dashed line represents the angular velocity of a CLV formatted disk showing a gradual decrease in angular velocity with increasing radius.
FIG. 2B is a graph representing changing linear velocity of the ZCLV disk 1. As seen in FIG. 2B, an innermost track of each zone is at a reference linear velocity Vr, and linear velocity increases towards each outer track in each zone.
FIG. 2C represents sector lengths within each zone of ZCLV disk 1. The sector lengths in FIG. 2C are equivalent at an innermost track of each zone and are increasing with increasing radius in each zone. FIG. 2D illustrates a recording/reproducing frequency utilized in recordings on ZCLV disk 1. The recording/reproducing frequency is shown at a constant level throughout each zone.
In more detail, the relation between a track positioned at a particular radius of ZCLV disk 1 and angular velocity is shown in FIG. 3. FIG. 3 shows zone 1 between radius R1 and R2, zone 2 between radius R2 and R3, and zone 3 between radius R3 and R4. The angular velocity for each zone is shown on a vertical axis. As seen in FIG. 3, the angular velocity remains constant within each zone, but changes between zones. Because the angular velocity within each zone remains constant, the linear velocity within each zone changes according to radius.
FIG. 4 illustrates linear velocity according to radius for three zones (zone 1, zone 2 and zone 3) of the ZCLV disk 1. The innermost radius (or track) of each zone is at a constant reference linear velocity Vr. The linear velocity increases throughout the zone to a final velocity representing a ratio of the radii of outer to inner tracks of each respective zone applied against the reference linear velocity Vr ((R2/R1)Vr, for zone 1, for example).
When ZCLV format is applied to a disk of which a recording area is contained within radii between 20 mm and 60 mm, which is almost the same as CD (compact disk) and DVD (digital video disk), the disk is divided into 10-20 zones. Since the linear velocity at any particular track within each respective zone is in proportion to the innermost radius of the respective zone versus the radius of the particular track within the respective zone, and each subsequent zone begins at an increased radius reducing the proportion thus described, a variance in linear velocity within a zone is approximately 10% to 20% for the case of an inner zone and approximately 3% to 7% in the case of an outer zone. This variance in linear velocity within a zone is represented by the slopes of lines representing linear velocity in each zone in FIG. 4 (zone 1 corresponding to an inner zone, and zone 3 corresponding to an outer zone). The differences in change of linear velocity between zones (between 3% and 20%) are accounted for because of the varying ratios between the innermost radius and all other radii within a same zone.
The recording process is complicated by the changing linear velocities within zones of ZCLV disk 1. In order to make high quality recordings, the recording power is required to be in proportion to the linear velocity. Therefore, the recording power must be increased as linear velocity increases within a zone, and high quality recording cannot be achieved via a single recording power when utilizing a ZCLV formatted disk.
The present inventor has realized that in order to achieve high quality recording on a ZCLV formatted disk, the recording power must be controlled in proportion to a radius within each zone as shown in FIG. 5. FIG. 5 is a graph having a vertical axis corresponding to estimated recording power and a horizontal axis corresponding to radii for each of three zones on ZCLV disk 1. The recording power in the innermost track within each zone is P0. The recording power at an outermost track within each zone is required to be set in proportion to the outer and inner radii times P0 (such as (R2/R1)P0 for zone 1, for example). P0 is an amount of power recommended by the disk manufacture but may not correspond to an optimum recording power because of differences in individual disks or machine characteristics.
When Optimum Power Control (OPC) is intended to be achieved, it is necessary to optimize recording power in accordance with a combination of a disk media and a disk driving apparatus because of variances in material and manufacture of the media and driving apparatus. However, in a ZCLV formatted disk, since the linear velocity is different within each zone and therefore the recording characteristic within each zone are also different, OPC cannot be achieved by a single optimum recording power which, in the case of CLV formatted disks, is obtained in only one test recording area as explained above.
The present inventor has realized that a laser recording power optimizing method is needed that can be applied to ZCLV formatted optical disks such that OPC can be maintained throughout each zone of a ZCLV formatted disk. The method should also account for recording characteristics of the disk media and disk driving apparatus, and therefore allow for high quality recordings.